The US Department of Energy (DOE), through the National Reactor Innovation Centre (NRIC), has awarded $3.9m to Radiant, Ultra Safe Nuclear Corporation (UNSC) and Westinghouse to design experiments to test microreactor designs in the planned Demonstration of Microreactor Experiments (DOME) test bed at Idaho National Laboratory (INL).

The awards will enable the three companies to advance their microreactor designs through a front-end engineering & experiment design (FEEED) process. that supports developers in planning for the design, fabrication, construction, and testing of fuelled reactor experiments.

“The FEEED process will bring three microreactor designs – Kaleidos [Radiant], Pylon [USNC], and eVinci [Westinghouse – one step closer to reality” said Assistant Secretary for Nuclear Energy Dr Kathryn Huff. “These technologies will give choices to diverse communities looking to transition to a clean energy future.”

Microreactor designs typically produce 1-20 MWt for use directly as heat or converted to electric power. They are described by their designers as being suitable to power independent microgrids, restore power in emergency situations, or supply remote communities that currently rely on diesel generators.

DOME is being developed by repurposing the Experimental-Breeder Reactor-II containment structure as a new test bed intended to speed up microreactor development. DOE says testing in DOME could start in 2026. DOE is also developing the Laboratory for Operation & Testing in the US (LOTUS) test bed, intended to host smaller reactor experiments to support the development of advanced reactors.

NRIC, launched by DOE in 2020, is developing both DOME and LOTUS and also developed the FEEED process to help industry partners progress more quickly toward first-of-a-kind testing of advanced reactors. NRIC, led by INL, facilitates collaboration between developers and the US National Laboratory System. NRIC says it is “charged with and committed to demonstrating advanced reactors by the end of 2025”.

Above: Radiant’s portable zero-emissions microreactor

California-based start-up Radiant Industries was set up in 2019 by former SpaceX engineers. Its Kaleidos design is a high-temperature gas-cooled reactor (HTGR) which will use TRISO fuel, a helium coolant, and a graphite moderator. All components will be fitted in a single shipping container to facilitate rapid deployment. It is designed to produce 1.2MWe or 1.9 MWt for heating or water desalination, as a potential replacement for diesel generators.

Earlier this year Radiant announced that it had raised $40m in a Series B funding round led by Andreessen Horowitz, bringing its total capital raised to $54m with an additional $2.3m in government awards. In December 2022 Radiant was awarded a voucher under the DOE Office of Nuclear Energy Gateway for Accelerated Innovation in Nuclear (GAIN) scheme. GAIN voucher recipients do not receive direct financial awards but provide funding to DOE national laboratories to help businesses overcome critical technological challenges to commercialising their technologies. Argonne National Lab will work with Radiant Ito perform numerical modelling of heat production and removal in its microreactor concept.

Radiant says its primary focus is on a demonstration at INL’s DOME facility no later than 2026 and is targeting commercial unit production in 2028. However, this seems ambitious as the reactor is only in the design stage and so far the only operating HTGR in the world is in China. Regulatory approvals could also prove problematic and there is no guarantee that DOME will be operating by 2026.

Above: Pylon's TRISO-fuelled transportable micro reactor

USNC’s Pylon microreactor is a 10-tonne containerised system designed to produce 1.5-5 MWe – smaller than the company's Micro Modular Reactor (MMR) HTGR system. It is designed to be easily transportable to off-grid locations both on Earth and in space: for terrestrial use, the system is intended to fit in a standard container. Pylon is based on USNC’s MMR and Fully Ceramic Micro-encapsulated (FCM) fuel technologies.

The Pylon D1 Demonstration System design, slated for DOME testing, contains a small HTGR with FCM fuel, metal hydride neutron moderator, and graphite control drums. “Pylon D1 uses helium to transfer the fission generated heat through the primary coolant loop to a secondary gas loop (helium, air, supercritical CO2, and other gases) for ejection into the surrounding environment. USNC is planning to use the results of the demonstration to support development of the MMR.

USNC has active micro reactor deployment projects in Canada at the Canadian Nuclear Laboratories in Chalk River, in the USA at the University of Illinois Urbana-Champaign, and at LUT University in Lappeenranta, Finland and in Poland. Additional projects are under development in the USA, Canada, and Europe. A 15 MWt (5 MWe) demonstration plant is planned for Chalk River. Site preparation and construction is expected to begin in 2025, subject to the necessary approvals, for operation in 2027, which may be optimistic.

Above: The eVinci microreactor designed by Westinghouse

Westinghouse’s eVinci microreactor design is a transportable reactor that is fully factory built, fuelled and assembled, and capable of delivering combined heat (up to 13 MWt) and power (up to 5 MWe). Its small size allows for standard transportation methods and rapid, on-site deployment, with superior reliability and minimal maintenance, making it suitable for use in remote locations. It will use TRISO fuel. It is one of several advanced reactor designs being supported through DOE’s Advanced Reactor Demonstration Project (ARDP) to help accelerate the development and deployment of new reactor technologies.

Westinghouse is also developing its Nuclear Test Reactor (NTR) which it aims to operate by 2026. The NTR will be “one-fifth scale representation” of an eVinci microreactor. Westinghouse says the eVinci technology is 100% factory built and assembled before it and will be shipped in a container to site.

Westinghouse recently announced the launch of a new design and manufacturing facility in Pittsburgh to accelerate commercialisation of the eVinci microreactor. In June, Westinghouse established eVinci Technologies as a separate business unit within the company to streamline all aspects of bringing the microreactor to the market.

Above: The Experimental-Breeder Reactor-II containment structure will become a new test bed intended to speed up microreactor development

Testing of these reactors will depend on DOME being completed and operational. The EBR-II operated from 1964 to 1994, and was originally built to demonstrate a complete sodium-cooled breeder reactor power plant. It was later modified to test other reactor designs and to test materials and fuels for fast reactors, as well as generating power and heat for the site. The reactor and much of its supporting equipment has been dismantled, but the containment structure remains – 80 feet high with a diameter of 70 feet. DOE says it is well suited to host reactor demonstration and other nuclear projects.